Generally speaking, computer renderings of objects with surface texture are more interesting and realistic than those without texture. Texture mapping is a technique that adds an appearance of surface detail by wrapping or projecting a digitized texture image onto a computer generated surface. Digitized textures can be obtained from a variety of sources, e.g., cropped from a photo CD image as a texture "chip", but the resulting texture chip may not have a desired size or shape corresponding to a surface that is to be textured. Furthermore, to cover a large object, an image rendering system may need to repeat the texture; this can lead to unacceptable artifacts either in the form of visible seams, visible repetition, or both.
Texture mapping suffers from an additional fundamental problem; often there is no natural map from the (planar) texture image to the geometry/topology of the surface, so the texture may be distorted unnaturally when mapped. There are some partial solutions to this distortion problem but there is no universal solution for mapping an image onto an arbitrarily shaped surface.
An alternative to texture mapping is to create (paint) textures by hand directly onto a computer generated, three-dimensional surface model, but this process is both labor intensive and requires considerable artistic skill.
Another alternative is to use computer-synthesized textures so that as much texture can be generated as needed to cover a particular surface. Furthermore, some of the synthesis techniques produce textures that tile seamlessly.
Using synthetic textures, the distortion problem has been solved in two different ways. First, some techniques work by synthesizing texture directly on the object surface. The second solution is to use so-called "solid textures". A solid texture is a three-dimensional array of color values. A point on the surface of an object is colored by the value of the solid texture at the corresponding three-dimensional point. Solid texturing can be a very natural solution to the distortion problem; there is no distortion because there is no mapping. However, existing techniques for synthesizing solid textures can be quite cumbersome. One must learn how to "tweak" the parameters or procedures of the texture synthesizer to get a desired effect.
Therefore, a need exists in the art for a method and apparatus for generating textures that can cover, without seams or significant distortion, surfaces of any size.